Structural and Electrical Properties of Sintered Zinc-titanate Ceramics

Poster presented at the ELECTROCERAMICS X, June 18-22, 2006, Toledo, Spai

Control system modeling of hydraulic actuator with compressible fluid flow

U radu su tretirane Rimanove parcijalne diferencijalne jednačine u obliku izraza (1) gde je promenljiva μ definisana relacijom (2). Odgovarajući granièni uslovi definisani su u različitim oblicima, kao što su granični uslovi pritiska i protoka i to na fiksnim i na pokretnim granicama. Problem je formulisan sa ciljem da opiše kompletnu dinamiku hidrauličkog aktuatora, uključujući njegov stvarni protok i geometrijske karakteristike. U tu svrhu napravljen je poseban algoritam i odgovarajući računarski paket za simulaciju kompletne dinamike hidrauličkog aktuatora, uključujući i prisutne efekte talasa. Za rešenje problema korišćena je metoda karakteristika. Rezultati računarske simulacije dinamike hidrauličkog aktuatora predstavljeni su 3-D dijagramima.The paper treats Riemann's partial differential equations in the form (1), where variable μ is defined by relation (2). Corresponding boundary conditions are defined in various forms, such as boundary conditions of pressure and flow on the fixed and movable boundaries. Problem formulation is constructed in order to describe hydraulic actuator dynamics in a complete form, including its real flow and geometric characteristics. Special algorithm is generated and a corresponding computer package for simulation of the complete hydraulic actuator dynamics, including the existing wave effects, using the method of characteristics to obtain the desired problem solution. Results of computer simulation of hydraulic actuator dynamics are presented in 3-D diagrams

Control system modeling of hydraulic actuator with compressible fluid flow

U radu su tretirane Rimanove parcijalne diferencijalne jednačine u obliku izraza (1) gde je promenljiva μ definisana relacijom (2). Odgovarajući granièni uslovi definisani su u različitim oblicima, kao što su granični uslovi pritiska i protoka i to na fiksnim i na pokretnim granicama. Problem je formulisan sa ciljem da opiše kompletnu dinamiku hidrauličkog aktuatora, uključujući njegov stvarni protok i geometrijske karakteristike. U tu svrhu napravljen je poseban algoritam i odgovarajući računarski paket za simulaciju kompletne dinamike hidrauličkog aktuatora, uključujući i prisutne efekte talasa. Za rešenje problema korišćena je metoda karakteristika. Rezultati računarske simulacije dinamike hidrauličkog aktuatora predstavljeni su 3-D dijagramima.The paper treats Riemann's partial differential equations in the form (1), where variable μ is defined by relation (2). Corresponding boundary conditions are defined in various forms, such as boundary conditions of pressure and flow on the fixed and movable boundaries. Problem formulation is constructed in order to describe hydraulic actuator dynamics in a complete form, including its real flow and geometric characteristics. Special algorithm is generated and a corresponding computer package for simulation of the complete hydraulic actuator dynamics, including the existing wave effects, using the method of characteristics to obtain the desired problem solution. Results of computer simulation of hydraulic actuator dynamics are presented in 3-D diagrams

Aeronautical Engineering

Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of flight vehicle. Consequently, they are usually the products of various technological and engineering disciplines including aerodynamics, propulsion, avionics, materials science, structural analysis and manufacturing. These technologies are collectively known as aerospace engineering. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering. It is typically a large combination of many disciplines that makes up aeronautical engineering. The development and manufacturing of a modern flight vehicle is an extremely complex process and demands careful balance and compromise between abilities, design, available technology and costs. Aeronautical engineers design, test, and supervise the manufacture of aircraft. They also develop new technologies for use in aviation. Aeronautical Engineering is a chapter that encompasses challenging areas such as aircraft design, light-weight structures, stability and control of aeronautical vehicles, propulsion systems, and low and high speed aerodynamics. The field also covers their aerodynamic characteristics and behaviors, airfoil, control surfaces, lift, drag, and other properties. The chapter will include all our research and published papers

Defectoscopy of direct laser sintered metals by low transmission ultrasonic frequencies

This paper focuses on the improvement of ultrasonic defectoscopy used for machine elements produced by direct laser metal sintering. The direct laser metal sintering process introduces the mixed metal powder and performs its subsequent laser consolidation in a single production step. Mechanical elements manufactured by laser sintering often contain many hollow cells due to weight reduction. The popular pulse echo defectoscopy method employing very high frequencies of several GHz is not successful on these samples. The aim of this paper is to present quadraphonic transmission ultrasound defectoscopy which uses low range frequencies of few tens of kHz. Therefore, the advantage of this method is that it enables defectoscopy for honeycombed materials manufactured by direct laser sintering. This paper presents the results of testing performed on AlSi12 sample. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057

Characterization of NTC thick film thermistor paste Cu0.2Ni0.5Zn1.0Mn1.3O4

A powder of Cu0.2Ni0.5Zn1.0 Mn1.3O4 composition for custom thermistor was prepared by using the respective mixture of metal oxides and solid state reaction at 1000 °C/4h in air. The obtained thermistor powder was milled in the planetary ball mill and agate mill for a prolonged time to achieve submicron powder. The prepared thermistor powder was further characterized by using XRD and SEM techniques. After that, the thermistor powder was pressed into small disc-shaped samples and sintered at 1150 °C/2h. The sintered samples were also characterized by using XRD and SEM. The main electrical properties such as nominal resistance R and thermistor exponential factor B were measured in the climatic test chamber. After that, the thick film paste was prepared using the same powder, an organic vehicle and a glass frit. The paste was printed on alumina substrate, dried at 150 °C /30 min and sintered in air at 850 °C /10 min in a hybrid conveyor furnace. Planar electrodes were printed on the sintered NTC thermistor layer using PdAg thick film paste. The electric properties of the sintered thick film thermistor were also measured in the climatic test chamber. The obtained results were used for development of novel self-heating thermistor applications

Optimal Design and Control of Multi-Motor Drive System for Industrial Application

In this paper, the topology of the adjustable speed drive with active front end rectifier is considered in terms of application in multi-motor drives. A dynamic model of the rectifier with a coupled LCL filter is presented. A simulation model has been developed for the analysis of multi-motor drive system dynamics and power flow. Based on the simulation model, the functional possibilities of reversible induction motor drive with active front end converter and multiple voltage source inverters on a common DC bus at the motor side are analysed. One example of the application of a complex full regenerative multi-motor drive system on a common DC bus for an industrial crane, implemented with Siemens converters, is shown. The motor and generator mode of operation from the aspect of energy saving as well as the influence of drives on the distribution network from the aspect of higher harmonics and power factors are analysed. Siemens\u27s original software, Starter commissioning tool, for drives configuration and data acquisition is used

Advanced structural testing methods for small wind turbines blade up to failure

Ovaj rad prezentuje statičko testiranje strukture kompozitne lopatice W55RBVS vetrogeneratora snage do6kW. Testiranje je bazirano na statičkom testiranju strukture do trenutka loma lopatice. Glavni cilj testiranja je definisanje krutosti lopaticeW55RBVS, određivanje maksimalne sile koja dovodi do loma kao i relativni razmah loma lopatice. Kompozitne lopatice W55RBVS, proizvedene u firmi WING.d.o.o., a ugrađuju se na dvokraki vetrogenerator Eoltec Scirocco. Ovaj test je definisan standardom IEC 61400-2. Ispitivanje lopatica je izvršeno u Laboratoriji za aerotehniku Mašinskog fakulteta Univerziteta u Beogradu. Test opterećenja se izvodi do momenta loma lopatice.Rezultat testiranja će biti iskorišćen za redizajniranje lopatice W55RBVS.This work demonstrates static testing of a composite blade W55RBVS structure for the wind turbines of up to 6kW power. The testing consists of the static testing of the structure up to the moment of the blade failure. The main purpose of the testing is to define and directly verify the rigidity of the blade W55RBVS,to determine the maximum force which leads to failure and the relative span of the blade failure. W55RBVS composite blades, manufactured by the company WING. doo and are installed on a two-blades wind turbine Eoltec Scirocco. This test is defined in the standard IEC 61400-2 /8/. Blade testing is performed in the Aerotechnics Laboratory of the Faculty of Mechanical Engineering, Belgrade University. The load test is performed up to the moment of the blade failure. The result of the testing will be used in order to improve the design of the blade W55RBVS

Structural features of near equiatomic FeCo-2V semi-hard magnetic alloy prepared by MIM technology

The structural properties of a magnetically semi-hard near equiatomic FeCo-2wt%V (FeCoV) alloy produced by Powder Injection Moulding (PIM) (option by fine metal powder - Metal Injection Moulding (MIM) technology) were investigated in this paper. Starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology was completed by high-temperature sintering for 3.5 hours at temperatures from 1370 OC to 1460 OC in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics. The influence of sintering temperature was investigated concerning the aspects of the processes of structural transformation by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The appearance of an intense diffraction peak of the α'-FeCo phase (crystal structure type B2) was registered for all investigated samples. Structural parameters particle size Dmax, Feret X, and Feret Y exhibit constant increase with increase of sintering temperature

Advanced structural testing methods for small wind turbines blade up to failure

Ovaj rad prezentuje statičko testiranje strukture kompozitne lopatice W55RBVS vetrogeneratora snage do6kW. Testiranje je bazirano na statičkom testiranju strukture do trenutka loma lopatice. Glavni cilj testiranja je definisanje krutosti lopaticeW55RBVS, određivanje maksimalne sile koja dovodi do loma kao i relativni razmah loma lopatice. Kompozitne lopatice W55RBVS, proizvedene u firmi WING.d.o.o., a ugrađuju se na dvokraki vetrogenerator Eoltec Scirocco. Ovaj test je definisan standardom IEC 61400-2. Ispitivanje lopatica je izvršeno u Laboratoriji za aerotehniku Mašinskog fakulteta Univerziteta u Beogradu. Test opterećenja se izvodi do momenta loma lopatice.Rezultat testiranja će biti iskorišćen za redizajniranje lopatice W55RBVS.This work demonstrates static testing of a composite blade W55RBVS structure for the wind turbines of up to 6kW power. The testing consists of the static testing of the structure up to the moment of the blade failure. The main purpose of the testing is to define and directly verify the rigidity of the blade W55RBVS,to determine the maximum force which leads to failure and the relative span of the blade failure. W55RBVS composite blades, manufactured by the company WING. doo and are installed on a two-blades wind turbine Eoltec Scirocco. This test is defined in the standard IEC 61400-2 /8/. Blade testing is performed in the Aerotechnics Laboratory of the Faculty of Mechanical Engineering, Belgrade University. The load test is performed up to the moment of the blade failure. The result of the testing will be used in order to improve the design of the blade W55RBVS